Spark Control System: Description

The Spark Delay Timing Control System is used to reduce HC and NOx emissions by delaying vacuum to distributor advance unit during acceleration.

Fig 1: Spark Delay Timing Control System (Schematic)

This system consists of delay valve which reduces vacuum advance during acceleration mode. Calif. models are also equipped with a water thermo valve which prevents advance until engine coolant temperature is above 122°F (50°C).